.idml was probably your best hope inside ID. Can you select the objects by doing a select all? Not sure waht I would do after that, but it would maybe help us to narrow the problem. Also check to be sure the layer isn't locked, and that something unexpected hasn't found it's way into the file.
Do you have a backup copy of the file? If not, you may need to weigh the cost of rebuilding against the cost of Markzware's recovery service (Bad InDesign or Quark File Recovery Submission Form). David Dilling from Markzware was offering forum users, on a trial basis, a discount on their first file recovery if they mentioned that they found the service here (link to this page), but I don't know if the offer is still valid.
Thanks Peter. The layer wasn't locked, and I was not able to select the objects. I found something even more strange: when I hit "go link" on one of the links on the corrupted pages, the X and Y coordinates, as well as the H and W, contained 10+ digit numbers (in front of the decimal.) I tried changing them back to something normal, but got an error message.
I ended up "go to link"-ing and deleting all the bad links and re-creating those twenty pages, because it had to get in to the printer today. Fortunately I had made a PDF from the file a couple of days ago, so I at least had a visual reference from which to re-construct.
Still a mystery, but I appreciate your response.
Abobe is so remarkably out of control for the sake of making new money. These applications should be as dependable and simple as a hammer to use - instead, they tend to break or screw up our workloads if we make one false move. The company is so clueless about the suffering they impart to those of us who have to get projects done ontime and billed. It's a heartless monopoly.